2,634. Denying One's Intention
Hilchos Shevuos 2:12
The same law (as in the previous halacha) also applies to the other types of oaths: one isn’t liable until his mouth and his heart are in agreement. Let’s say that someone took an oath not to eat and he ate. He was warned before eating, and he replied that he meant to say that he wouldn’t leave; he only misspoke and said that he wouldn’t eat. In such a case, he isn’t liable to lashes unless, before eating, he acknowledges in front of witnesses that the intention of his oath was to prohibit eating, or if he accepts the warning without objecting at that time. If he objects later, we don’t pay any attention. Let’s say that he was warned and he denied taking an oath or a vow at all. The witnesses testify that he took an oath or vow, and he responds that he did, but his mouth and his heart were not in agreement, or that he had certain conditions in mind. In such a case, we don’t listen to him and he is liable to lashes.
Hilchos Shevuos 2:13
Similarly, if witnesses tell a man that his wife took a vow and he replies that he intended to nullify the vow and he in fact did so, we accept his word. If he’s told that she took a vow and he denies it, but when they testify against him, he says that his intention was to nullify the vow, his word is not accepted.